The present invention relates generally to power converters and, more particularly, to a lossless gate driver circuit for MOS-gated power switching devices in high-frequency applications.
In a conventional gate driver circuit, energy stored in the gate capacitance of a switching device is dissipated in the internal and external gate resistors during turn-on and turn-off of the switching device. For example, for a 1200V/600A trench gate insulated gate bipolar transistor (IGBT) switching at 62 kHz, the power loss can be as high as 9 W and is mainly dissipated in the external gate resistor of the IGBT. High-power, low-inductance, high-cost resistors are thus needed to implement the external gate resistance, and additional heat sinking or cooling is typically required.
Accordingly, it is desirable to provide a substantially lossless gate driver circuit for power switching devices in high-frequency applications, while providing desirable turn-on and turn-off voltage levels and controllable gate voltage slew rate. It is further desirable that such gate driver circuit have the capability of recycling the gate charge and thereby achieve substantially lossless gate control.
A resonant gate driver circuit suitable for driving power switches in high-frequency applications recovers gate drive energy stored in the gate capacitance of the power switches, resulting in substantially lossless operation. In a preferred embodiment, the resonant gate driver circuit provides bipolar gate control signals that are compatible with PWM operation.
In an exemplary resonant gate driver circuit for driving a power switching device, on-state and off-state voltage sources are coupled in series with each other, the series combination of voltage sources being coupled across a half-bridge configuration of on-state and off-state switching devices. A clamp diode is coupled across each on-state and off-state switching device, respectively. A resonant inductor is coupled between the junction joining the switching devices and the junction joining the clamp diodes. The gate of the power switching device is coupled to the resonant inductor at the junction joining the clamp diodes. The junction between the on-state and off-state voltage sources is connected to the emitter of the power switch.
In operation, energy stored in the gate capacitance is transferred to the resonant inductance during each switching event (i.e., turn on or turn off) of the power switch; and the stored energy is subsequently recovered by the on-state and off-state voltage sources in the same switching event of the power switching device.